This application claims the priority from Korean Patent Application No. 2003-88795, filed on Dec. 8, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method of encrypting a motion picture file and a method of managing digital rights using the same, and more particularly, to a method of encrypting a motion picture file while maintaining the format of the motion picture file so that a streaming service under digital rights management is possible, and a method of digital rights management using the encryption method.
2. Description of the Related Art
Currently, service providers provide multi-media data to users in the form of download service or streaming service. Download service enables an entire multi-media file to be downloaded from a service provider's computer to a user's computer and then reproduced. Streaming service is when a service provider segments a file into real-time refreshable segments and transmits the segments to a user who reproduces the segments in real-time.
Whichever service is provided by the service provider, the user has to complete a process of acquiring legitimate rights for relevant multi-media data before being able to reproduce the files. A user who attempts to access the files without acquiring legal rights to the files should be blocked. To facilitate such selective provision and denial of access, multi-media files are encrypted.
Digital rights management (DRM) is a solution for all sorts of systems that only allow users with legal rights to access encrypted files. Generally, a DRM system includes a contents provider, a user, a DRM server, and so on, and can include an electronic payment process, a user authentication process, and a public key infrastructure (PKI).
The most basic DRM method is encrypting a Motion Picture Experts Group (MPEG) file, transmitting the encrypted MPEG file to a user, and then providing a key that can decrypt the encrypted file to the user if it is confirmed through a user authentication process that the user has legal rights. The user authentication process can include an electronic payment process and a PKI can be used for transmitting the key.
However, such an encryption method cannot be used for streaming service because decryption is possible only after downloading the entire file. That is, even if a user key is transmitted from the DRM server, reproduction of the corresponding file is not possible until the entire encrypted file is downloaded.
Another encryption method involves encrypting discrete cosine transform coefficients, for example, AC or DC values, during a motion picture file encoding process.
This method, however, does not encrypt a completed motion picture file but adds an additional encryption process to a motion picture file encoding process. As a result, this method cannot be easily applied to a completed motion picture file. In addition, if a contents provider has to apply an encryption algorithm that is specifically designated for the contents provider in a motion picture file production process, the contents provider has the disadvantage of having to depend on a motion picture file provider to provide the service. This inhibits the growth and development of the on-line contents industry.